The present invention relates generally to fluid pumps which controllably send a very small amount of fluid from a nozzle hole in a nozzle plate, and more particularly to a fluid pump which is manufactured by adhering the nozzle plate to a chamber which accommodates and ejects fluid.
The fluid pump of the present invention is especially suitable for heads of inkjet printers (i.e., inkjet heads), which are universally used as general printers, or copiers, facsimile machines, computer systems, and word processors, and a combination thereof that have a printing function.
Structurally speaking, among inkjet printers, some are manufactured by adhering a nozzle plate having a nozzle hole through which ink is sent, to a chamber that accommodates ink. Some inkjet heads using a piezo-electric element, for example, have recently become more and more popular due to its good energy efficiency. The inkjet heads of this type adhere a nozzle plate to a pressure chamber, and jet ink by raising pressure in the pressure chamber using deformation of the piezo-electric element.
The above inkjet head typically is made by connecting a nozzle plate to a three-layer structure including a pressure-chamber plate having a pressure chamber, a thin plate, and a piezo-electric element. The pressure chamber is formed by a concave groove in the pressure-chamber plate and the thin plate. The piezo-electric element is arranged opposite to the pressure chamber on the thin plate.
The piezo-electric element has internal and external electrodes. When voltage is applied from the external electrode to the internal electrode, i.e., when the piezo-electric element is charged, it deforms so that it can compress the pressure chamber via the thin plate, and returns to the original state as a result of removal of the voltage (or discharge). The thin film transmits the deformation of the piezo-electric element to the pressure chamber. Thus, voltage application from the external electrode to the internal electrode deforms the piezo-electric element and compresses the pressure chamber via the thin film, whereby ink is ejected from the pressure chamber through the nozzle hole. Recently, in order to achieve high resolution images by narrowing a pitch between adjacent nozzle holes, a piezo-electric element that has a layered structure and is divided into a plurality of parts has been increasingly utilized.
The realization of high-resolution images requires not only narrowing a adjacent-nozzle-hole pitch but also precisely jetting ink from a nozzle hole in a predetermined direction. In addition, the nozzle plate should be firmly secured to the three-layer structure. However, it is difficult to adhere the three layers to one another and form the three-layer structure so that the three layers are aligned with a nozzle connection surface that is a surface to which the nozzle plate is connected. Accordingly, the conventional art polish the edge of the three-layer structure before the nozzle plate is connected to the three-layer structure, to form a flat nozzle connection surface.
Part of the external electrode of the piezo-electric element is cut off by the polishing process, and thus reconstructed at the nozzle connection surface by a vacuum evaporation. Then, the adhesive agent is applied, and the nozzle plate is adhered to the nozzle connection surface while the nozzle hole is aligned with the nozzle hole. The inkjet head is completed in this way. After the inkjet head is completed, ink is filled up in the pressure chamber.
It is thus necessary to polish and smooth the nozzle connection surface in manufacturing such a fluid pump that adheres the nozzle plate to the chamber which accommodates fluid. Nevertheless, the conventional manufacturing method is disadvantageous because the polishing process breaks mechanically or electrically a member at and/or near the nozzle connection surface, or requires an arduous reconstruction.
For instance, in the above inkjet head, the piezo-electric element is generally fragile, in particular, the piezoelectric element which has a layered structure easily suffers from exfoliation, crack, and chip-off as a result of polishing at the nozzle connection surface. In addition, a polishing speed which should set to be slow so as to minimize breaking of the piezoelectric element through polishing delays the manufacturing time.
Moreover, the external electrode of the piezoelectric element should formed before the polishing to inspect a characteristic (or yield) of the piezoelectric element and adhere the piezoelectric element that passes the inspection to the thin plate. However, it is cut off by the polishing, and reconstructed inconveniently after the polishing.
On the other hand, a fluid pump which adheres a nozzle plate to a fluid chamber has a disadvantage in that ink leaks from the nozzle connection surface due to bad adhesion of the nozzle plate or cracks of adhesive agent applied onto the nozzle connection surface.
For example, in the above inkjet head, the internal electrode tends to short-circuit since ink penetrates into the inside when ink is filled up in the pressure chamber or in another condition. This problem is particularly remarkable where the piezo-electric element is divided by grooves.
Accordingly, it is a general object of the present invention to provide a novel and useful fluid pump and a method of manufacturing the pump in which the above disadvantages are eliminated.
Another and more specific object of the present invention is to provide a fluid pump and a method of manufacturing the pump which not only protect a member in the neighborhood of the nozzle connection surface but also shorten the manufacturing time.
In order to achieve the above object, an inkjet head of the present invention comprises a pressure-chamber plate which forms a pressure chamber for accommodating ink, a piezo-electric element which may compress the pressure chamber in the pressure-chamber plate, a protective layer, connected to the piezo-electric element, which protective layer forms at least part of a nozzle connection surface and spaces the piezo-electric element from the nozzle connection surface, and a nozzle plate having a nozzle hole which jets the ink in the pressure chamber when the piezo-electric element compresses the pressure chamber, the nozzle plate being connected to the nozzle connection surface.
Another inkjet head of the present invention comprises a piezo-electric element which forms a pressure chamber for accommodating ink, and may compress the pressure chamber, a protective layer, connected to the piezo-electric element, which protective layer forms at least part of a nozzle connection surface and spaces the piezo-electric element from the nozzle connection surface, and a nozzle plate having anozzle hole which jets the ink in the pressure chamber when the piezo-electric element compresses the pressure chamber, the nozzle plate being connected to the nozzle connection surface.
Another inkjet head of the present invention comprises a piezo-electric element which forms a pressure chamber for accommodating ink, and may compress the pressure chamber, the piezo-electric element having first and second internal electrodes, a protective layer, connected to the piezo-electric element, which protective layer shields the second internal electrode from the first internal electrode, and forms at least part of a nozzle connection surface, and a nozzle plate having a nozzle hole which jets the ink in the pressure chamber when the first and second internal electrodes are electrified and a potential difference occurs between the electrodes, enabling the piezo-electric element to compress the pressure chamber, the nozzle plate being connected to the nozzle connection surface.
Another inkjet head of the present invention comprises a pressure-chamber plate which forms a pressure chamber for accommodating ink, and forms at least part of a nozzle connection plate, a piezo-electric element, spaced from the nozzle connection surface, which may compress the pressure chamber in the pressure-chamber plate, and a nozzle plate having a nozzle hole which jets the ink in the pressure chamber when the piezo-electric element compresses the pressure chamber, the nozzle plate being connected to the nozzle connection surface.
A method of manufacturing an inkjet head of the present invention comprises the steps of adhering to one another a pressure-chamber plate which forms a pressure chamber for accommodating ink, a thin film, and a piezo-electric element which may compress the pressure chamber of the pressure-chamber via the thin film, forming a protective layer at least onto the piezo-electric element, polishing the protective layer and forming a nozzle connection surface at least onto the protective layer, and connecting to the nozzle connection surface a nozzle plate which has a nozzle hole which jets the ink in the pressure chamber when the piezo-electric element compresses the pressure chamber.
A fluid pump of the present invention comprises a first member which accommodates fluid, a second member, connected to the first member, which ejects the fluid accommodated in the first member, a protective layer, connected to the second member, which protective layer forms at least part of a nozzle connection surface and spaces the second member from the nozzle connection surface, and a nozzle plate having a nozzle hole which jets the fluid from the second member, the nozzle plate being connected to the nozzle connection plate.
Thus, the inkjet head of the present invention spaces the piezo-electric element from the nozzle connection surface by the protective layer, and thus does not suffer from ink leakage and other damages. In addition, according to the method of manufacturing the inkjet head, the protective layer protects the piezo-electric element from being broken by polishing.
Other objects and further features of the present invention will become readily apparent from the following description and accompanying drawings.